Underground Gas Storage Glossary - Innovative Energy Consulting ...

Innovative Energy Consulting Pty Ltdcapacity per year and is typical of gas reticulation companies serving aresidential heating load. This type of storage is ofen referred to as 1 cycle or 180day storage.Bedded Salt: Bedded Salt refers to either a relatively thin layer or a combinationof stacked thin layers of underground salt. Bedded Salt is not nearly as attractiveas Salt Domes for the creation of caverns for the purposes of gas storage.Caverns created in Bedded Salt tend to be smaller and of irregular shapes andsizes, thereby costing more on a per working gas capacity basis and resulting ina less stable pressure vessel.Brining: See Solution MiningBuffer Zone: A subsurface zone that extends beyond the mapped reservoir poolboundary or at least beyond the Gas Cap Boundary acquired by an UGSoperator to ensure adequate protection against exploration and productionactivity that might conflict in the future with the actual reservoir boundaries or asurface zone that extends beyond the surface area required for storage relatedsurface facilities acquired by an UGS operator in order to prevent future conflictover incompatible uses of the land, noise complaints, odour complaints, etc. Thedifficulty of recovering escaped gas, physically or financially argues for amplebuffer zones around the estimated boundaries of the UGS pool or formations.Caprock: Sealing formation overlying a Porous Storage Pool that prevents gasmigration. While the porosity and permeability of the Caprock is very low, it doesexist and consequently a small and often negligible amount of Injected Gas maybe absorbed in the Caprock under Delta-Pressuring conditions.Cavern Convergence: Reduction in geometrical cavern volume caused by e.g.salt creeping. The annual reduction of the geometrical cavern volume isexpressed by the convergence rate.Cavern Creep: The phenomena whereby the salt walls of a salt cavern slowlyflow due to stresses associated with either the cycling of natural gas or due totectonic activity. Also refers to the natural self-sealing characteristic of saltwhereby fissures or fractures created by drilling and dissolution processes willheal and a sound permeability seal will be reestablished in a relatively short timeframe.Cavern Fill Rate: The time it would take to fill the cavern based on the workinggas capacity and the injection capacity – usually 20 days.Cavern Spacing: The spacing between any two salt caverns should besufficient to prevent any risk of the caverns communicating over time. Theminimum Cavern Spacing for salt caverns used for cycling natural gas isUnderground Gas Storage Terminology 2